The backlight module is a critical component for liquid crystal display (LCD) panels because the liquid crystal does not emit light itself. A backlight module is mainly used for providing a light source with enough brightness and evenly distributed so that an LCD panel can display images normally. As LCD panels are widely used in electronic products such as monitors, notebook computers, digital cameras and projectors, etc., the demands for backlight modules and related components are growing continuously.
Generally speaking, the backlight module is divided into two types, which are the direct-type backlight module and the edge-type backlight module. In the direct-type backlight module, a backlight source, such as a fluorescent lamp, is disposed right under the backlight module. Two or more than two fluorescent lamps can be used for enhancing the brightness of the light source. Therefore, it is suitable for using in a display panel which requires a higher degree of brightness or with a larger size, such as LCD monitors or LCD televisions. On the other hand, in the edge-type backlight module, a light source generator is disposed on a lateral side of a display panel, and the light produced by the light source generator is evenly guided in the display panel by a light guide plate (LGP). Therefore, the size and cost of the liquid crystal display can be reduced. The edge-type backlight module is applied to small sized electrical products.
FIG. 1 is an illustration of a conventional edge-type backlight module. An edge-type backlight module 9 comprises a printed circuit board 910, a light emitting diode 920, a reflective film 940, a light guide plate 950 and a reflective surface 930.
The light emitting diode 920 is disposed on a left side of the printed circuit board 910 and the reflective film 940 is disposed on a right side of the printed circuit board 910. The light guide plate 950 is disposed on the reflective film 940 so that the reflective film 940 is disposed between the light guide plate 950 and the printed circuit board 910. The reflective surface 930 is disposed on a side edge of the light guide plate 950 and is kept a distance from the light emitting diode 920. The reflective surface 930 is used for reflecting the light emitted by the light emitting diode 920. In the assembling, because of cutting tolerances of the reflective film 940, assembling tolerances of the reflective film 940, and assembling deviations of the light emitting diode 920, the length of the reflective film 940 is shorter than the length of the light guide plate 950.
FIG. 2 is an illustration of the conventional edge-type backlight module and a light path. When the light emitting diode 920 emits a light beam 960, the light beam 960 is reflected onto the printed circuit board 910 by the reflective surface 930. The light beam 960 is then reflected onto the light guide plate 950 by the printed circuit board 910. Because the light beam 960 entered into the light guide plate 950 does not satisfy the angle of total reflection, the light beam 960 is emitted from the light emitting surface of the light guide plate 950. Therefore, hot spots are occurred which will seriously affect the image quality.
Therefore, in order to solve the above problems, a backlight module and a liquid crystal display using the same are required. The backlight module can reduce light which does not satisfy the angle of total reflection entering into the light guide plate.